A known pressure sensitive stylus of the type to which the improvement of the present invention is directed is disclosed in U.S. Pat. No. 4,786,764 (now Re 34,095), Padula et al, the contents of which are incorporated herein by reference.
A typical assemblage of a stylus and a digitizer tablet is illustrated in FIG. 1, wherein a stylus 20, for example of the type disclosed in U.S. Pat. No. Re 34,095, or of the type of the present invention, is adapted to be pressed against a conventional digitizer table 21. The stylus may be coupled to a control circuit 22, such as a computer, via a cable 23, or the coupling may be made without direct cables, for example via conventional radio or light wave transmission. It will be understood of course that such coupling techniques to a control circuit are also applicable to the present invention.
The stylus disclosed in U.S. Pat. No. Re 34,095 includes a "refill" that is axially movable within a sleeve, the refill having one end protruding from the stylus and being adapted to be pressed against the surface of a digitizer table. The other end of the refill is positioned to apply axial pressure against a pressure sensitive resistance element, such as, for example only, an FSR (a known force sensitive transducer ink). The pressure sensitive resistance element is coupled to a circuit which may be external of the stylus, to enable a determination to be made of the amount of pressure being applied to the surface by the user of the stylus. This pressure can be used by an application program operating on a computer to determine whether the user is selecting an option on the screen or tablet surface, similar to a "mouse click" operation. Or, in graphic design applications, the measurement of the pressure can be used to effect a change in a parameter, such as the width of the "paint brush" being used.
The term "refill", as employed in U.S. Pat. No. Re 34,095 was exemplified by a conventional metal refill element for a pen. In order to avoid any erroneous connotation that this term is restricted to such a metal refill element, it is replaced herein by the term "tip" element. The term "tip" element, as used hereinafter, refers to an elongated tip element, which may be conductive or nonconductive, and which is fabricated to effect the transfer of pressure on the exposed tip of the tip element to a pressure sensitive resistance element. The term "tip" element thus includes refill elements of the type disclosed in the above patent.